AFP officers executed the warrants, which had been sought by the Registered Organisations Commission to ensure documents weren't tampered with or destroyed.

Minister for Employment Michaelia Cash during a Senate estimates hearing at Parliament House in Canberra on Wednesday 25 October 2017.

The Australian Federal Police has launched an investigation into the leaking of information about raids on two union offices, amid pressure on a federal minister to resign.

Prime Minister Malcolm Turnbull is standing by his employment minister, despite calls for her to step aside over her office's role in tipping off media about Tuesday's police raids on the Australian Workers' Union.

Michaelia Cash says she hasn't considered resigning after admitting to giving wrong evidence to a Senate committee.

Senator Cash told the estimates committee on Wednesday on five occasions neither she nor her office had anything to do the media tipoff.

She also personally told the prime minister she had not been the leaker.

But on Wednesday evening she announced her senior media adviser had resigned after revealing he had informed journalists of the raids on the AWU's Sydney and Melbourne offices.

Labor says she should resign or be sacked.

Meanwhile an AFP spokesman told AAP the agency was investigating the "alleged unauthorised disclosure of information" about the raids.

AFP officers executed the warrants, which had been sought by the Registered Organisations Commission to ensure documents weren't tampered with or destroyed.

The ROC told the estimates hearing on Wednesday night the AWU had refused to hand over all the documents it had requested, however on Thursday it retracted the statement.

The commission is investigating $200,000 in donations made by the AWU, including $100,000 given to activist group GetUp in the 2005/06 financial year while now-Labor leader Bill Shorten was the union's secretary.

The AWU has lodged a freedom of information request with Senator Cash's office to try and determine exactly when she learned about the raids.